DE 100 07 317 A1 shows a stepless door check for a vehicle door. The door check comprises a spindle rod, which is connected to a vehicle body in an articulated manner at its one end and is accommodated in the vehicle door at its other end, where a braking and fixing device is arranged. The braking and fixing device is accommodated in a retaining housing, wherein the retaining housing surrounds the spindle rod substantially in a rotationally symmetrical manner. To this end, the spindle rod passes through a central cutout in the retaining housing. The spindle rod has an external thread which is engaged with an internal thread of a spindle nut, wherein the spindle nut is mounted in the retaining housing in a rotatable manner by means of a rolling bearing. If a tensile or compressive force is exerted on the spindle rod during an opening or closing process, this results in a rotary movement of the spindle nut. In a rest state of the door, a brake lining is urged axially against a contact face of the rotatable spindle nut by means of a spring force, such that the door is fixed in position. When energized, a longitudinally displaceable electromagnet, which is in the form of a coil arrangement in a housing, moves the brake surfaces counter to the direction of the force of the spring such that the brake lining is taken out of material contact with the spindle nut, with the result that the spindle nut can rotate freely and the vehicle door is no longer fixed in position but is released. In this case, the longitudinally displaceable electromagnet can be triggered by means of sensors.
DE 10 2007 026 796 A1 shows an electrically controllable door check for vehicle doors. A transmission housing that is passed through by a retaining rod embodied as a toothed rack is accommodated in a vehicle door, wherein the toothed rack is connected to the body via a bearing. The toothed rack is engaged with a gearwheel of the transmission housing, wherein this gearwheel is connected to a transmission gearwheel for conjoint rotation, said transmission gearwheel being engaged with a further gearwheel. Brake disks are arranged on an end side of the further gearwheel. A spring element is accommodated in a coil housing and spaces apart an end face of the coil housing, which is configured as a bearing surface, from the brake disks. Furthermore, an annular coil is arranged in the coil housing in an external region of the coil housing, whereas the spring element is arranged in an internal region of the coil housing. In this case, the brake disks and the coil housing are made of a magnetizable material. If the coil is energized, the material is magnetized to such an extent that the brake disks are pressed against the bearing surface of the coil housing, with the result that a friction fit is formed and the door does not move any further. Even when the energizing of the coil ends, the magnetizing is retained and the vehicle door is secured in its position such that only an oppositely energized coil spaces the brake disk apart from the bearing surface of the coil housing again and releases the arrested door. Provision is made for the energizing of the arrested door also to be triggered by external sensors.
DE 10 2011 056 225 A1 shows a stepless door check in which a transmission housing is secured in a retaining housing, wherein the retaining housing is fixed to a vehicle door. The door check comprises a spindle rod with a threaded portion and a thread-free end portion, wherein, in the region of its end portion, the spindle rod comprises a bearing point for pivotable connection to the body and an end stop in the region away from the end portion. In this case, the end stop limits a maximum opening travel of the vehicle door. A spindle nut, which is accommodated in a rotatable manner in the transmission housing, engages with an internal thread in an external thread of the spindle rod. In the region of the thread-free end portion, the spindle nut slides over the spindle rod. A displacement of the spindle nut over the spindle rod is designed to be as friction-free as possible, and so the vehicle door can fly open unintentionally, for example in the event of a gust of wind. In order to avoid this, the spindle nut is additionally provided with an external thread which engages in the manner of a bevel gear with a pinion of a force transmission element. A shaft connected to the force transmission element is connected to a cup-shaped friction element which is accommodated in a resilient manner in a pot-shaped brake surface. If the vehicle door is now moved, the spindle nut rotates about the spindle rod and in this case moves the spindle rod relative to the transmission housing by generated axial forces. At the same time, the rotation of the spindle nut sets the pinion into a rotary movement, since the pinion of the forces transmission element is coupled to an external thread of the spindle nut. As a result, the rotary movement is transmitted through the shaft to the cup-shaped friction element. A coefficient of friction between the cup-shaped friction element and the brake surface can be selected such that a movement of the door has a desired resistance and so, for example, a sudden gust of wind is not capable of unintentionally opening the vehicle door. The end portion of the spindle rod is provided so that, during a closing process of the vehicle door, the spindle nut does not have to rotate about the thread of the spindle rod along a final stretch, but rather can slide over the end portion such that a braking action cannot take effect and the vehicle door closes reliably.
DE 10 2011 106 664 A1 shows a stepless door check in which a retaining rod in the form of a spindle rod is mounted in an axially displaceable manner in a retaining housing. In this case, a spindle nut is accommodated in the retaining housing. The spindle nut is in this case mounted in the manner of a rolling bearing so as to be rotatable about an axis of rotation of the spindle rod, and has, on an inner side, a threaded bore which engages with a threaded bore of the spindle rod. The retaining housing comprises a permanent-magnetic material and a cavity which is formed coaxially with the axis of rotation of the spindle rod, such that an inner wall with a smaller radius of the retaining housing encloses the spindle rod and an outer wall with a larger radius is arranged further away from the axis of rotation of the spindle rod. The mutually facing sides of the inner wall and of the outer wall are magnetically polarized differently. By means of joints, magnetized brake jaws are articulated to the spindle nut, in a rotationally symmetrical manner in the cavity, in the direction of extension of the spindle rod and as a result can rotate about the spindle rod. The retaining housing and the brake jaws are formed in a permanent-magnetic manner such that, in a rest position of the vehicle door, the brake jaws are pressed by magnetic forces against the inner wall of the retaining housing, said inner wall being arranged in a rotationally symmetrical manner between the spindle rod and the retaining jaws. As a result of the brake jaws bearing against the inner wall, facing the spindle rod, of the retaining housing, a frictional force opposes a rotary movement of the spindle nut. As a result of a breakaway torque being overcome, the brake jaws are lifted off the inner wall of the housing by means of a centripetal force in spite of the magnetically attractive action, and are moved in a kind of floating state in the cavity between the inner wall and the outer wall. The outer wall of the housing is in the form of a permanent magnet such that the magnetic force thereof has a repellent action on the brake jaws. If the axial displacement of the spindle rod is noticeably increased, for example by a gust of wind, then the rotary speed of the spindle nut also increases, and as a result so does the centripetal force on the brake jaws, and so the repulsion of the outer retaining housing is overcome and the brake jaws pass into material contact with the outer wall on account of the increased centripetal force, with the result that a frictional force is generated which brakes the rotary speed of the spindle nut and thus also a displacement speed of the spindle rod. In this case, the door check functions on the principle of the centrifugal brake and works without any external energy supply.
DE 199 21 213 A1 shows a stepless vehicle door check in which a retaining housing is connected to a vehicle door or a body via a joint, and a spindle rod which passes through the middle of the retaining housing. The spindle rod is connected to the vehicle door or the vehicle body in a rotationally fixed manner. In an interior of the retaining housing, the spindle rod engages in a thread of a spindle nut, wherein the spindle nut is accommodated in a rotatable manner in a radial bearing. On both end sides of the retaining housing, two plate springs are supported on the two inner sides of the retaining housing in a direction of extension of the spindle rod, wherein the plate springs are supported with their concave sides on supporting faces of the retaining housing and are supported on the opposite convex sides on the spindle nut. Between the retaining housing and the plate springs, balls are arranged in ball races on the plate springs. In a rest position of the vehicle door, equilibrium of forces prevails at the plate springs in a direction of extension of the spindle rod, such that the spindle nut, which is subjected to an axial force on both sides by the plate springs, is located in a central position between the plate springs in the retaining housing. If a tensile or compressive force acts on the spindle rod, an axial force is transmitted to the spindle nut by a tooth engagement of the spindle rod with the spindle nut, such that, depending on the direction of displacement of the spindle rod, one of the two plate springs is pushed in the direction of the retaining housing by the spindle nut, with the result that a curvature of the particular plate spring is reduced. If the axial force is increased further, the ball acts like a fulcrum of a lever, such that a peripheral bearing face of the plate springs is lifted from the housing wall, and so the corresponding plate spring is no longer in direct contact with the retaining housing, with the result that a frictional force between the plate spring and the housing is reduced and the spindle nut is easier to rotate than at the start of a displacement process of the spindle rod. In this state, the plate springs are mounted on a corresponding retaining-house side only by means of the balls. As a result of this, when a vehicle door is opened, initially a greater force has to be applied, but after this greater force has been applied, a vehicle door is easier to open since the coefficient of friction between plate spring in the spindle nut is reduced. If the opening movement is interrupted, an axial force no longer acts on the plate spring, with the result that the plate spring moves the spindle nut back into a position in the middle of the retaining housing, with the result that the original coefficient of friction is reestablished and a stepless retaining position of the vehicle door is adopted. This functions both in an opening direction and a closed direction of the door.
DE 44 35 720 A1 and DE 198 32 502 C2 each show a stepless fixing device for a vehicle door, wherein, during a closing or opening process, a spindle rod with an external thread is moved through an internal thread of a rotatable spindle nut. In this case, the spindle nut is mounted in a rotatable manner on a bearing within a retaining housing. The spindle nut is engaged around by a cable, wherein the two cable ends are fastened to a pivot lever at one fastening point or a plurality of fastening points. The pivot lever is subjected to a force by a compression spring such that a pretensioning force is exerted on the cable. As a result of this pretensioning force, the cable is applied to the spindle nut such that brake torques are generated when the spindle nut rotates. By means of an electric motor which is controllable by external sensors, the pivot lever can be pivoted such that a tension of the cable about the spindle nut is released, with the result that the brake torques caused by the cable are minimized. In this state, fixing of the vehicle door is released and so the vehicle door can be closed or opened.